*4.13. Antioxidant Activity*

To evaluate the antioxidant activity of obtained ALG/G, ALG/G/xNZ, and ALG/G/ xTO@NZ films, 300 mg of each film were cut into small pieces and placed inside dark glass bottles with 10 mL of a 40 ppm ethanolic solution of diphenyl-1-picrylhydrazyl (DPPH). A dark glass bottle with 10 mL of ethanolic DPPH solution without the addition of any film was used as the reference sample. The absorbance at 517 nm wavelength of the DPPH solution was measured at 0 h and after 24 h incubation using a Jasco V-530 UV-vis spectrophotometer. For each kind of film, three different samples were measured and the statistical mean was achieved as the final measurement.

The % antioxidant activity after 24 h incubation of films was calculated according to the following equation:

$$\% \text{ Anioxidant activity} = \frac{\text{Abs}\_{\text{ref.}} - \text{Abs}\_{\text{sample}}}{\text{Abs}\_{\text{ref.}}} \times 100\tag{8}$$
